Technical Abstract:
Aggressiveness and mycelial compatibility groups (MCGs) of Sclerotinia sclerotiorum isolates from diverse hosts and geographic locations (diverse sampling) and from soybean at diverse locations (one Argentine and two USA, Illinois field samplings) were assessed. Thirteen MCGs were identified within the diverse sampling; one MCG consisted of six isolates, and 12 MCGs consisted of one isolate each. Five MCGs were identified within each Illinois field sampling, and nine MCGs were identified within the Argentine field sampling. MCGs were shared between the diverse sampling and both Illinois soybean field samplings, but no Argentine MCGs were shared with other samplings. Aggressiveness of isolates varied (P=0.05) within all samplings and within most MCGs. Mycelial incompatibility may perpetuate discrete genets or MCGs propagated either by vegetative, asexual reproduction or by homothallic, inbred, sexual reproduction, but aggressiveness levels varied within MCGs.